Headed bioabsorbable tissue anchor

ABSTRACT

A headed bioabsorbable tissue anchor has a continuous thread spiraling around a tapering central core. At the distal end, the headed bioabsorbable tissue anchor terminates in a flat point. At the proximal end, the bioabsorbable tissue anchor has a flat, disk-shaped head for engaging tissue, and slots formed in the head for engaging a driver. The headed bioabsorbable tissue anchor has a large thread surface per turn of thread. As the anchor is turned into bone for engaging cancellous bone, the disk-shaped head engages and anchors the tissue to the bone.

[0001] This application is a division of U.S. application Ser. No.09/469,177, filed Dec. 21, 1999, which is a continuation-in-part of U.S.application Ser. No. 08/954,206, filed Oct. 20, 1997, which is acontinuation of U.S. application Ser. No. 08/905,393, filed Aug. 4,1997, which claims the benefit of U.S. Provisional Application No.60/023,011, filed Aug. 5, 1996. This application also claims the benefitof U.S. Provisional Application No. 60/118,788, filed Feb. 4, 1999.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an apparatus and method forfixation of soft tissue to bone. More specifically, the presentinvention relates to sutureless arthroscopic apparatus and methods foranchoring soft tissue to bone using a headed bio-absorbable tissueanchor.

[0004] 2. Description of the Related Art

[0005] When soft tissue tears away from bone, reattachment becomesnecessary. Various fixation devices, including sutures, screws, staples,wedges, and plugs have been used in the past to secure soft tissue tobone. More recently, various types of threaded suture anchors have beendeveloped.

[0006] The known suture anchors generally require that the surgeon tieknots in the suture to secure tissue to the bone. Tying surgical knotsis tedious and time-consuming consuming. It would be preferable to beable to secure the soft tissue to the bone in one step without having totie knots.

[0007] Accordingly, a need exists for a bioabsorbable anchor for softtissue fixation that can be installed to secure tissue easily andeffectively without sutures. A need also exists for a soft tissuefixation device that displaces a minimum amount of bone upon insertion.In addition, a need exists for a tissue fixation device havingexceptional pull-out strength, especially in soft bone.

SUMMARY OF THE INVENTION

[0008] The present invention overcomes disadvantages of the prior art,such as those noted above, by providing a headed bioabsorbable tissueanchor having a thread spiraling helically around a central body, inwhich the head of the anchor engages the soft tissue for fixation tobone.

[0009] The headed bioabsorbable tissue anchor of the present inventionhas a cannulated, threaded central body. A flat, disk-shaped head isprovided on the proximal end of the anchor. The disk-shaped head engagessoft tissue for fixation as the anchor is installed through soft tissueand into bone.

[0010] The central body of the anchor tapers toward the distal end. Thedistal tip preferably is flat to avoid tip breakage, as could occur witha pointed tip.

[0011] The anchor is formed of a bioabsorbable PLA copolymer, preferablypoly (L/D-lactide) acid.

[0012] Surgical installation is achieved using a driver that engages thedisk-shaped head for installing the threaded anchor by turning into thebone. The anchor has at least one opening for engagement with the end ofa driver.

[0013] The outer circumferential dimension of the disk-shaped headadvantageously is substantially larger than the circumference of thecentral body. Accordingly, the enlarged head engages tissue and holds itin place against the bone into which the tissue anchor has beeninstalled.

[0014] Advantageously, the threads of the headed bioabsorbable tissueanchor of the present invention have a cancellous thread design thatprovides an increased percentage of thread surface area for each turn ofthe anchor, as compared with known anchors, thus providing increasedpull-out strength, and a decreased tendency for back-out. The cancellousthread design is similar to the metal suture anchor described in U.S.Pat. No. 6,214,031, issued Apr. 10, 2001, the entire disclosure of whichis incorporated herein by reference.

[0015] In addition to increased pull-out strength, the one piecesutureless design of the implant advantageously eliminates suturemanagement issues, and simplifies the arthroscopic surgical technique.Further, revisions are simplified, and the biocompatible PLA copolymermaterial will not interfere with MRI or CT scans. The wide, low profilehead provides a broad area of tissue to bone contact without impingementon other tissues. Also, the cannulated design allows the use of a guidewire to ensure accurate implant placement. The implant also can be usedin open procedures.

[0016] Other features and advantages of the present invention willbecome apparent from the following description of the invention, whichrefers to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a side elevation of a headed bioabsorbable tissue anchoraccording to the present invention.

[0018]FIG. 2 is a cut-away side elevation of the headed bioabsorbabletissue anchor if FIG. 1.

[0019]FIG. 3 is a perspective view of the headed bioabsorbable tissueanchor of FIG. 1.

[0020]FIG. 4 is an elevation of a driver according to the presentinvention.

[0021]FIG. 5 is an elevation of a tap according to the presentinvention.

[0022]FIG. 6 is an elevation of a 1.0 mm guide wire used forinstallation of the headed anchor according to the present invention.

[0023]FIG. 7 is an elevation of a spear used to facilitate insertion ofthe guide wire according to the present invention.

[0024]FIG. 8 is a perspective view of the tissue anchor of FIG. 1assembled onto the driver of FIG. 4 and disposed over the guide wire ofFIG. 6.

[0025]FIG. 9 is a schematic illustration of the tissue anchor of FIG. 1installed through tissue and into bone.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Referring to FIGS. 1-3, the headed bioabsorbable tissue anchor 2of the present invention includes a body 4 provided in the shape of acannulated, tapered cylinder. A continuous thread 6 wraps around body 4in a clockwise direction, as shown. The thread preferably has an outerdiameter of 5.0 mm. The outer diameter of the thread remainssubstantially constant, while the inner diameter of the thread decreasesdistally, following the taper of the body 4. Accordingly, the surfacearea of the thread increases distally. The central core of body 4preferably is circular in cross-section, and tapers from a maximumdiameter near the proximal end to a minimum diameter toward the distalend.

[0027] Headed bioabsorbable tissue anchor 2 is provided at the proximalend of body 4 with a head 10. The anchor is provided with at least oneopening for engaging a driver. Although many different drive couplingarrangements are possible, in the preferred embodiment of the invention,equally spaced arcuate slots 12 are formed in the disk-shaped head toengage the driver described more fully below. The driver is used fordelivery and installation of the anchor. Slots 12 formed in the head ofthe anchor preferably taper to enhance retention of the anchor on thedistal end of the driver. The head 10 is 8.0 mm in diameter to provide abroad area of tissue-to-bone contact, and has a smooth, low 1.5 mm thickprofile to minimize trauma to surrounding tissue.

[0028] At the distal tip 14, the anchor terminates in a flat end 16. Theflat end is less likely than a pointed tip to break off and become aloose body within the patient. Cannula 18 is provided centrally.Preferably, the cannula has a circular cross-section; however, thecannula could be shaped to engage a driver for installation of theanchor by turning. Accordingly, the cannula could be hexagonal orprovided with ridges, for example.

[0029] The head 10 preferably is separated from the thread 6 by a smoothsection 19 that passes through and accommodates the tissueatraumatically upon insertion of the anchor into bone, as described morefully below.

[0030] The anchor preferably is formed of a bioabsorbable, biocompatiblematerial. Preferably, the anchor material is a PLA copolymer, mostpreferably poly(L/D-lactide) acid (PLDLA) having a high inherentviscosity.

[0031] Anchor thread 6 has a proximal face 20, a distal face 22 and anedge. Near distal tip 14, the edge is formed at an acute angle to theproximal face so as to provide a V-shaped edge 24 that provides a betterpurchase on the bone as the anchor is advanced by turning duringinstallation. Proceeding proximally along the anchor thread, the threadwidens toward a U-shape and the edge becomes substantially parallel withthe central axis of the anchor to provide a flat edge 26. The thicknessof the thread 6 increases, preferably continuously, from the distal endto the proximal end, as the profile of the edge changes from the sharp Vedge 24 to the increasingly wider flat edge 26. The overallconfiguration provides a spiral wedge that enhances fixation.

[0032] Preferably, between two and three flights or turns of thread 6are provided along body 4, between the proximal end and the distal tip.Adjacent sections of each flight are separated by a gap that isdetermined by the number of turns per inch of the thread.

[0033] Increased surface area of the thread also is achieved in part byproviding an increased ratio of the outer diameter of the thread to theinner diameter of the thread along at least a portion of the anchor.Preferably, the ratio is between 2.25 and 2.75. Most preferably, theratio of the outer diameter to the inner diameter is at least 2.5 alongat least a portion of the thread.

[0034] In addition, the headed bioabsorbable tissue anchor has a higherthread pitch than prior art screws, thus increasing the area of threadfor each turn of the screw, which leads also to greater pull-outstrength and faster installation. Significantly, due to the increasedpitch, fewer turns are required to advance the headed bioabsorbabletissue anchor into position during installation of the device.Accordingly, the headed bioabsorbable tissue anchor is easy to install,and displaces less tissue material upon insertion than known anchors.

[0035] The pull-out strength and minimal tissue damage are enhanced bythe relatively compressed cross-sectional aspect of the thread,particularly in relation to the broad axial faces of the threads.Further, in contrast to the tapered central axis, the threads maintain asubstantially fixed outer diameter along their length.

[0036] Increased back-out resistance can be enhanced further by surfacefeatures, such as indentations or radial ridges, on the top and/orbottom faces of the screw threads. The surface features augment theengagement between the thread surfaces and the surrounding tissue oncethe headed bioabsorbable corkscrew is installed.

[0037]FIG. 4 illustrates a preferred headed bioabsorbable tissue anchordriver 30 according to the present invention. The driver 30 has acannulated shaft 32 attached to a cannulated handle 34. At the distalend of shaft 32 a head 36 includes three arcuate projections 38 whichengage the tapered, arcuate slots 12 formed in the head of the screw 2.

[0038]FIG. 5 illustrates a cannulated tap 40 according to the presentinvention. The tap 40 includes a shaft 42 and a handle 44. Tap 40 has atap head 46 provided on the distal end of the instrument. The tap head46 has a trocar tip 48 and thread 50 for entering and tapping bone priorto insertion of the bioabsorbable corkscrew 2. A depth stop 52 engagesthe tissue to indicate an appropriate depth of insertion, as describedbelow.

[0039] The configuration of the distal end of tap 50 is substantiallysimilar to the configuration of the threaded portion of the anchor,described above. Advantageously, the outer diameter of the thread 50 onthe tap is smaller than the outer diameter of the thread 6 on theanchor, typically by about 5%. Accordingly, the anchor thread 6compresses bone tissue as it is installed by turning into the threadformed by the smaller tap thread 50. The forced fit enhances fixationstrength. In a preferred embodiment, for example, the outer diameter ofthe tap thread is 5.0 mm, and the outer diameter of the tap thread is4.78 mm.

[0040] The present invention also provides an assembly of the headedbioabsorbable tissue anchor and the driver for installing the anchor.Referring to FIG. 8, the tissue anchor 2 is shown engaged on the end ofdriver 30. The assembly has been placed over a guide wire 60, asdescribed below with respect to a preferred method of installation.

[0041] Indications for the headed bioabsorbable tissue anchor of thepresent invention include rotator cuff repair (full or partial tears),Bankart repair, SLAP lesion repair, biceps tenodesis, acromio-clavicularseparation repair, deltoid repair, and capsular shift or capsulolabralreconstruction in the shoulder; lateral stabilization, medialstabilization, achilles tendon repair, hallux valgus reconstruction,midfoot reconstructions, and metatarsal ligament repair in thefoot/ankle; medial collateral ligament repair, lateral collateralligament, patellar tendon repair, posterior oblique ligament repair, andiliotibial band tenodesis in the knee; scapholunate ligamentreconstruction, ulnar collateral ligament reconstruction, and radialcollateral ligament reconstruction in the hand/wrist; and biceps tendonreattachment, tennis elbow repair, and ulnar or radial collateralligament reconstruction in the elbow.

[0042] Referring to FIGS. 6-9, an illustrative, generalized method ofsecuring soft tissue to bone using the headed bioabsorbable tissueanchor of the present invention received over a guide wire 60 isdescribed as follows:

[0043] 1. Prepare a bone bed site 62 by debriding the site with ahigh-speed bur or rasp.

[0044] 2. Move the tissue 64 into the proper position apposing theprepared bone site 62.

[0045] 3. Install a 1.0 mm guide wire 60 by advancing the guide wirethrough the tissue 64 and into the prepared bone bed 62 at anappropriate angle. See FIG. 6. Installation of the guide wire can befacilitated by inserting the guide wire through a cannulated spear 70(FIG. 7) that has been used to pierce the tissue and firmly engage thebone surface with its pointed tip.

[0046] 4. Place the cannulated tap 40 over the exposed guide wire 60 andadvance by turning through the tissue and into the bone. The tap isadvanced until the depth stop collar 52 depresses the tissue. Remove thetap by turning in the direction opposite to installation, while holdingthe guide wire in place.

[0047] 5. Place the headed tissue anchor over the guide wire. Place thecannulated driver over the guide wire to engage the head of the anchor.See FIG. 8.

[0048] 6. Advance the anchor by turning clockwise through the tissue andinto the bone until the head of the implant depresses the tissue. SeeFIG. 9.

[0049] 7. Repeat the installation steps, inserting additional anchors atother tissue locations for further fixation, as needed.

[0050] 8. Remove the guide wire.

[0051] Accordingly, in a preferred method of rotator cuff repair, forexample, the rotator cuff is retracted laterally and the spear 70 isinserted through the tendon. The guide wire 60 is advanced by turninginto the debrided portion of the humerus. The tap, aligned over theguide wire, is turned through the tendon and into bone until the collarslightly depresses the tendon. During tap removal, a guide wire pusher(not shown) inserted into the back of the tap is used to keep the guidewire in place. The cannulated anchor is placed over the guide wire andatraumatically turned using a driver through the tendon into bone untilthe cuff is firmly apposed against bone. The guide wire is removed.

[0052] The broad apposition and compression of soft tissue to boneprovided by the present invention speeds healing and provides a strongersoft tissue fixation, compared to sutures. Concurrently, the smoothupper surface of the anchor head 10 allows atraumatic articulation ofthe repaired joint. The cancellous thread provides enhanced threadpurchase through the outer cortical bone layer. The anchor of thepresent invention withstands up to 90 pounds of pull-out force prior tofailure. In addition, the PLA copolymer (PLDLA) material has a highinherent viscosity, and in degradation studies the anchor retains 90% ofits fixation strength after 12 weeks.

[0053] Although the present invention has been described in relation toparticular embodiments thereof, many other variations and modificationsand other uses will become apparent to those skilled in the art.Therefore, the present invention is to be limited not by the specificdisclosure herein, but only by the appended claims.

What is claimed is:
 1. A method of rotator cuff repair using a headedbioabsorbable tissue anchor having a cannulated body having a distal endand a proximal end, a continuous thread disposed in a spiral around thebody and having an outer diameter; and a disk-shaped head disposed onthe proximal end of the body and having an outer diameter greater thanthe outer diameter of the thread, the anchor having at least one openingformed in the anchor for engaging a driver, the method comprising thesteps of: forming a hole in bone; engaging the tissue anchor with atissue anchor driver; and installing the headed tissue anchor throughtissue and into the hole formed in the bone such that the head of thetissue anchor engages the tissue and fixates the tissue to the bone asthe anchor is turned and advanced into the bone.
 2. The method of claim1, wherein the step of forming the hole in bone includes tapping threadsin the side of the hole for accepting the threads of the tissue anchor.3. The method of claim 1, wherein the step of forming the hole in bonecomprises the steps of: installing a guide pin into the bone; advancinga cannulated tap over the guide pin; and turning the cannulated tap intothe bone to form the hole.
 4. The method of claim 3, further comprisingthe steps of: removing the cannulated tap from over the guide pin; andadvancing the anchor over the guide pin to the hole formed in the bone.